Selecting the right electrical wire is a critical decision that balances safety, code compliance, and budget. Among the many options, one type consistently stands out for its proven reliability and versatility: THHN wire. If you’re specifying wiring for a construction project or an industrial application, the name THHN is bound to appear on your shortlist. THHN wire is also commonly used in machine tools, control circuits and some appliances.
THHN is a thermoplastic, high-heat-resistant, nylon-coated wire. It is rated for a maximum operating temperature of 90°C in dry locations. The meaning of each letter in THHN is as follows:
A nylon jacket plays a key protective role at both the physical and chemical levels. It resists abrasion during conduit pulling, shields against hydrocarbons like oil, and prevents punctures or accidental cuts to the inner insulation.
Qifan THHN wire is suitable for both indoor and outdoor applications where long-term reliability is essential. Its UL approval for permanent installation makes it a preferred choice for new construction and other projects requiring durable, set-and-forget wiring. When using THHN wire for outdoor and buried applications, it must be installed in conduit as it is not UV-resistant or waterproof on its own.
Thermoplastic and thermoset are two types of cable insulations commonly used for single conductors. THHN/THWN-2 is a thermoplastic product, whereas XHHW-2 is a thermoset product.
When designing and building a new facility, machine, or appliance, informed decisions depend on an understanding of their differences.
| Type | Temperature Rating | Minimum Installation Temp | Maximum Short Circuit Temp | Jacket |
| THHN | 90°C/ 194° F in dry and 75° C/ 167° F in wet environments | -10° C/ 14° F | 150° C/ 302° F | PVC insulation with nylon |
| THWN-2 | 90°C/ 194° F in both dry and wet environments | -10° C/ 14° F | 150° C/ 302° F | PVC insulation with nylon |
| XHHW-2 | 90°C/ 194° F in both dry and wet environments | -40° C/ -40° F | 250° C/ 482° F | XLPE |
THHN/THWN-2 uses thinner PVC insulation, which is prone to current leakage and dielectric breakdown under demanding chemical or environmental conditions. It also emits toxic smoke when burned and becomes less flexible in cold temperatures. However, thinner PVC insulation makes this kind of product lighter and less expensive.
XHHW-2 is a thermoset wire with XLPE (crosslinked polyethylene) insulation, offering superior resistance to chemicals and abrasion compared to PVC. In the event of a fire, XLPE emits significantly less toxic smoke than PVC. Additionally, thermoset materials like XHHW-2 provide greater flexibility, making them advantageous for installations requiring complex bends.
Qifan’s THHN product is very popular. Most of our customers find that our THHN product is perfectly suitable for their needs and it is less expensive.
On the other hand, our XHHW product is like the premium option: it’s tougher, lasts longer, and performs better in the long run. If you want extra reliability, it might be worth the investment.
